checks to establish running condition?

[mike-evans]

Hi guys, bought myself a 2001 yz 250 2t to get back into mx after 5 years out. The guy i bought it off said it has recently had re-plated cylinder, new piston and rings, new con rod, re-conned crank, new crank bearings and seals, new clutch plates and basket,, new stator, rear suspension bushes, chain and sprockets etc...all with receipts and approx 3 months old, i have only rode it twice and seems to ride fine, if anything i aint riding it hard enough yet..it does smoke alot on start up so i have just repacked the silencer, which produced some soaking oil covered black packing, also i find it hard to start. The plug (new, ridden with twice) isa nice brown tan colour, and has lots of compression, which does give hell of a kick back now and again when trying to start it. Is there checks i can undertake to see how the engine is? i.e things to take apart and look at/for etc to understand the engine condition? The reason i ask is because i bought a DOG of a yz 125 before and had nothing but trouble.....